1. Field of the Invention
The present invention relates generally to laser support structures, and more particularly to an optical and mechanical structure for laser support which is specially designed to prevent misalignment of laser optical components due to thermal gradients.
2. Background of the Invention
A major problem in space optics and in particular laser technology is that of maintaining the proper focal distances among optical components and in maintaining precise system alignment. Focal distances are critical to proper laser operation and must be maintained within close tolerances which can easily be exceeded by expansions and contractions in laser support structures caused by the existance of thermal gradients.
Thermal gradients of quite a substantial magnitude can occur in outer space, for example, where orbiting laser systems may be partially maintained at a very low temperature and partially heated by direct solar radiation or by the thermal output of the systems themselves. Accordingly, the neutralization of thermal gradients is an especially acute problem in extraterrestrial laser technology.
A number of apparatuses have been disclosed for providing thermally stable laser structures. One such device is disclosed in U.S Pat. No. 3,553,604 to Andress et al., issued Jan. 5, 1971. This patent discloses a laser support or holding device mounted within a housing having good heat conductivity and wherein the holding device itself is surrounded with heat insulating material for maintaining the temperature of the holding device constant along the axis of a laser. Similarly, U.S. Pat. No. 3,484,718 to Foster, issued Dec. 16, 1969, discloses a stabilized laser structure. The apparatus described in this patent includes an outer tubular support made from a material having a low coefficient of expansion, and an expansible tubular spacer within the outer support made from a material having a high coefficient of expansion. The proportionally opposed expansions between the spacer and the support are used to maintain uniform spacing between the laser mirrors. U.S. Pat. Nos. 3,808,553 and 3,793,595 to Locke et al and Russo et al, respectively, also disclose other thermally stabilized laser structures. However the devices disclosed in these patents, as well as all other known laser support structures, are generally deficient in that they are either too costly or complex to manufacture conveniently, or they do not provide a sufficient degree of thermal stability to meet the most exacting standards and thus fail to perform adequately in severe environments such as outer space. Accordingly there is a need for a further improvement in thermally compensated laser support structures.